1. Field of the Invention
The present invention relates to a data processing system, such as an electronic filing system, which processes data in connection with an optical disc and prints out the processing results in the form of a hard copy by a printer.
2. Description of the Related Art
Recent offices and factories produce a tremendous amount of documents and drawings. To file those documents and drawings, an electronic filing system using an optical disc has been recently developed and put into practical use. The electronic filing system optically stores the literal and graphic information contained in documents and appropriately processes the literal and graphic data. In the filing system, the information, which are optically picked up by a scanner or read out of an optical disc, may be displayed by a CRT display or printed out by a printer. Such a system is shown in U.S. Pat. No. 4,661,988, for example.
In one type of printer, a printer generates a horizontal sync signal and sends it to a host computer (main processor in a filing system). The host computer processes image data containing literal and graphic data in synchronism with the received horizontal sync signal. The printer receives and prints out such data.
In another type of printer, a printer sends a dot clock signal to a host computer. The host computer processes the image data, and sends the processed image data to the printer. The printer receives and prints out the image data.
An electronic filing system compatible with two different types of printers as mentioned above requires two types of interfaces, one for re-synchronizing a clock signal in the host computer by a horizontal sync signal supplied from the printer and the other for a dot clock signal supplied from the printer. Alternatively, it selectively uses two types of hardware in place of the above two different interfaces. In use, one type of hardware is selected in accordance with a printer used, and matches the printer to an interface circuit contained.
As described above, the conventional electronic filing system needs two types of interfaces or hardware installed inside or outside the host computer. This indicates that the filing system is expensive.